I'm developing a power supply circuit which has high and low voltage and a common ground. I have isolation of the switching control line via an optoisolator and a separate low voltage power supply. See attached circuit.

The remaining linking factor is the common ground - I have placed a diode to block any current flowing into the low voltage section.

Alternatively I could remove the linking ground connection all together.

Thank for your replies. Attached is the circuit with the optoisolator.

ErnieM: The part of the circuit for particular comment was using a barrier diode for the common DC ground. I would welcome further comment on the optoisolation and with hands and fingers away I do hope for no smoke or smoking confetti.

I have planned this circuit to drive a 3kW resistive heating element. The control of the mosfet is through another board which uses a PIC18F4620 and one of the PWM outputs. The full circuit also has a temperature bridge (for feedback loop), buttons, lcd screen and serial comms (TX&RX).

tubeguy: No transformers needed here as i'm not isolating from the mains supply, just a large amount of noisy switching. As per above, there a lot to the full circuit but once complete without smoking i'll happily share.

I intend to add an inductor to help with switching spikes (if I need to).